In addition, European colonialism was thrown off a relatively (historically speaking) short length of time after it happened in most places-- a century or three in most regions, quite often less. And so the damages of being conquered were still quite fresh, but the assimilation that inevitably happens over a long period of time-- such as the extension of full Roman citizenship to Gaul, the Romanized Seleucid dynasty of Judaea, etc.-- didn't happen. The conquered fought for and achieved independence before the original wounds had had a chance to heal, and the initial wounds had been very bad indeed because of the specific racial doctrines and calculated exploitation of the colonies on the part of the European powers. The Romans spoke and wrote of non-Romans as uncivilized, as barbarian, as incomprehensible, as unlucky enough not to have been born in Rome; the Catholic conquerors of the Caribbean decided that quite a few of the natives didn't have souls and consequently weren't human at all. You do not get the rhetoric of the colonized as essentially inhuman before the conquest of the Americas.